scholarly journals Axenic Biofilm Formation and Aggregation bySynechocystisPCC 6803 is Induced by Changes in Nutrient Concentration, and Requires Cell Surface Structures

2018 ◽  
Author(s):  
Rey Allen ◽  
Bruce E. Rittmann ◽  
Roy Curtiss
Keyword(s):  
Cell Surface ◽  
Biofilm Formation ◽  
Molecular Mechanisms ◽  
Type Iv Pili ◽  
Surface Structures ◽  
Biofuel Production ◽  
Phototrophic Biofilm ◽  
Phototrophic Biofilms ◽  
Type Iv ◽  
Cell Surface Structures

AbstractPhototrophic biofilms are key to nutrient cycling in natural environments and bioremediation technologies, but few studies describe biofilm formation by pure (axenic) cultures of a phototrophic microbe. The cyanobacteriumSynechocystissp. PCC 6803 (hereafterSynechocystis) is a model micro-organism for the study of oxygenic photosynthesis and biofuel production. We report here that wild-type (WT)Synechocystiscaused extensive biofilm formation in a 2000 liter outdoor non-axenic photobioreactor under conditions attributed to nutrient limitation. We developed a biofilm assay and found that axenicSynechocystisforms biofilms of cells and extracellular material, but only when induced by an environmental signal, such as by reducing the concentration of growth medium BG11. Mutants lacking cell surface structures, namely type IV pili and the S-layer, do not form biofilms.To further characterize the molecular mechanisms of cell-cell binding bySynechocystis, we also developed a rapid (8 hour) axenic aggregation assay. Mutants lacking Type IV pili were unable to aggregate, but mutants lacking a homolog to Wza, a protein required for Type 1 exopolysaccharide export inEscherichia coli, had a super-binding phenotype. In WT cultures, 1.2x BG11 induced aggregation to the same degree as 0.8x BG11. Overall, our data support that Wza-dependant exopolysaccharide is essential to maintain stable, uniform suspensions of WTSynechocystiscells in unmodified growth medium, and this mechanism is counter-acted in a pili-dependent manner under altered BG11 concentrations.ImportanceMicrobes can exist as suspensions of individual cells in liquids, and also commonly form multicellular communities attached to surfaces. Surface-attached communities, called biofilms, can confer antibiotic resistance to pathogenic bacteria during infections, and establish food webs for global nutrient cycling in the environment. Phototrophic biofilm formation is one of the earliest phenotypes visible in the fossil record, dating back over 3 billion years. Despite the importance and ubiquity of phototrophic biofilms, most of what we know about the molecular mechanisms, genetic regulation, and environmental signals of biofilm formation comes from studies of heterotrophic bacteria. We aim to help bridge this knowledge gap by developing new assays forSynechocystis, a phototrophic cyanobacterium used to study oxygenic phototsynthesis and biofuel production. With the aid of these new assays, we contribute to the development ofSynechocystisas a model organism for the study of axenic phototrophic biofilm formation.

scholarly journals Axenic Biofilm Formation and Aggregation bySynechocystissp. Strain PCC 6803 Are Induced by Changes in Nutrient Concentration and Require Cell Surface Structures

2019 ◽  
Vol 85 (7) ◽  
Author(s):  
Rey Allen ◽  
Bruce E. Rittmann ◽  
Roy Curtiss
Keyword(s):  
Biofilm Formation ◽  
Molecular Mechanisms ◽  
Type Iv Pili ◽  
Biofuel Production ◽  
Oxygenic Photosynthesis ◽  
Phototrophic Biofilm ◽  
Bg11 Medium ◽  
Phototrophic Biofilms ◽  
Type Iv ◽  
Cell Surface Structures

ABSTRACTPhototrophic biofilms are key to nutrient cycling in natural environments and bioremediation technologies, but few studies describe biofilm formation by pure (axenic) cultures of a phototrophic microbe. The cyanobacteriumSynechocystissp. strain PCC 6803 (hereSynechocystis) is a model microorganism for the study of oxygenic photosynthesis and biofuel production. We report here that wild-type (WT)Synechocystiscaused extensive biofilm formation in a 2,000-liter outdoor nonaxenic photobioreactor under conditions attributed to nutrient limitation. We developed a biofilm assay and found that axenicSynechocystisforms biofilms of cells and extracellular material but only when cells are induced by an environmental signal, such as a reduction in the concentration of growth medium BG11. Mutants lacking cell surface structures, namely type IV pili and the S-layer, do not form biofilms. To further characterize the molecular mechanisms of cell-cell binding bySynechocystis, we also developed a rapid (8-h) axenic aggregation assay. Mutants lacking type IV pili were unable to aggregate, but mutants lacking a homolog to Wza, a protein required for type 1 exopolysaccharide export inEscherichia coli, had a superbinding phenotype. In WT cultures, 1.2× BG11 medium induced aggregation to the same degree as 0.8× BG11 medium. Overall, our data support that Wza-dependent exopolysaccharide is essential to maintain stable, uniform suspensions of WTSynechocystiscells in unmodified growth medium and that this mechanism is counteracted in a pilus-dependent manner under altered BG11 concentrations.IMPORTANCEMicrobes can exist as suspensions of individual cells in liquids and also commonly form multicellular communities attached to surfaces. Surface-attached communities, called biofilms, can confer antibiotic resistance to pathogenic bacteria during infections and establish food webs for global nutrient cycling in the environment. Phototrophic biofilm formation is one of the earliest phenotypes visible in the fossil record, dating back over 3 billion years. Despite the importance and ubiquity of phototrophic biofilms, most of what we know about the molecular mechanisms, genetic regulation, and environmental signals of biofilm formation comes from studies of heterotrophic bacteria. We aim to help bridge this knowledge gap by developing new assays forSynechocystis, a phototrophic cyanobacterium used to study oxygenic photosynthesis and biofuel production. With the aid of these new assays, we contribute to the development ofSynechocystisas a model organism for the study of axenic phototrophic biofilm formation.

scholarly journals FppA, a Novel Pseudomonas aeruginosa Prepilin Peptidase Involved in Assembly of Type IVb Pili

2006 ◽  
Vol 188 (13) ◽  
pp. 4851-4860 ◽  
Author(s):  
Sophie de Bentzmann ◽  
Marianne Aurouze ◽  
Geneviève Ball ◽  
Alain Filloux
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Cell Surface ◽  
Molecular Mechanisms ◽  
Type Iv Pili ◽  
Reading Frame ◽  
Type Iv ◽  
Bacterial Aggregation ◽  
Epithelial Cell Surface ◽  
Prepilin Peptidase ◽  
Pilus Assembly

ABSTRACT Several subclasses of type IV pili have been described according to the characteristics of the structural prepilin subunit. Whereas molecular mechanisms of type IVa pilus assembly have been well documented for Pseudomonas aeruginosa and involve the PilD prepilin peptidase, no type IVb pili have been described in this microorganism. One subclass of type IVb prepilins has been identified as the Flp prepilin subfamily. Long and bundled Flp pili involved in tight adherence have been identified in Actinobacillus actinomycetemcomitans, for which assembly was due to a dedicated machinery encoded by the tad-rcp locus. A similar flp-tad-rcp locus containing flp, tad, and rcp gene homologues was identified in the P. aeruginosa genome. The function of these genes has been investigated, which revealed their involvement in the formation of extracellular Flp appendages. We also identified a gene (designated by open reading frame PA4295) outside the flp-tad-rcp locus, that we named fppA, encoding a novel prepilin peptidase. This is the second enzyme of this kind found in P. aeruginosa; however, it appears to be truncated and is similar to the C-terminal domain of the previously characterized PilD peptidase. In this study, we show that FppA is responsible for the maturation of the Flp prepilin and belongs to the aspartic acid protease family. We also demonstrate that FppA is required for the assembly of cell surface appendages that we called Flp pili. Finally, we observed an Flp-dependent bacterial aggregation process on the epithelial cell surface and an increased biofilm phenotype linked to Flp pilus assembly.

scholarly journals Role ofCaulobacterCell Surface Structures in Colonization of the Air-Liquid Interface

2019 ◽  
Vol 201 (18) ◽  
Author(s):  
Aretha Fiebig
Keyword(s):  
Cell Surface ◽  
Caulobacter Crescentus ◽  
Three Dimensional ◽  
Liquid Interface ◽  
Type Iv Pili ◽  
Surface Structures ◽  
Aquatic Environments ◽  
Content Type ◽  
Type Iv ◽  
Air Liquid Interface

ABSTRACTIn aquatic environments,Caulobacterspp. can be found at the boundary between liquid and air known as the neuston. I report an approach to study temporal features ofCaulobacter crescentuscolonization and pellicle biofilm development at the air-liquid interface and have defined the role of cell surface structures in this process. At this interface,C. crescentusinitially forms a monolayer of cells bearing a surface adhesin known as the holdfast. When excised from the liquid surface, this monolayer strongly adheres to glass. The monolayer subsequently develops into a three-dimensional structure that is highly enriched in clusters of stalked cells known as rosettes. As this pellicle film matures, it becomes more cohesive and less adherent to a glass surface. A mutant strain lacking a flagellum does not efficiently reach the surface, and strains lacking type IV pili exhibit defects in organization of the three-dimensional pellicle. Strains unable to synthesize the holdfast fail to accumulate at the boundary between air and liquid and do not form a pellicle. Phase-contrast images support a model whereby the holdfast functions to trapC. crescentuscells at the air-liquid boundary. Unlike the holdfast, neither the flagellum nor type IV pili are required forC. crescentusto partition to the air-liquid interface. While it is well established that the holdfast enables adherence to solid surfaces, this study provides evidence that the holdfast has physicochemical properties that allow partitioning of nonmotile mother cells to the air-liquid interface and facilitate colonization of this microenvironment.IMPORTANCEIn aquatic environments, the boundary at the air interface is often highly enriched with nutrients and oxygen. Colonization of this niche likely confers a significant fitness advantage in many cases. This study provides evidence that the cell surface adhesin known as a holdfast enablesCaulobacter crescentusto partition to and colonize the air-liquid interface. Additional surface structures, including the flagellum and type IV pili, are important determinants of colonization and biofilm formation at this boundary. Considering that holdfast-like adhesins are broadly conserved inCaulobacterspp. and other members of the diverse classAlphaproteobacteria, these surface structures may function broadly to facilitate colonization of air-liquid boundaries in a range of ecological contexts, including freshwater, marine, and soil ecosystems.

scholarly journals Myxococcus xanthus dif Genes Are Required for Biogenesis of Cell Surface Fibrils Essential for Social Gliding Motility

2000 ◽  
Vol 182 (20) ◽  
pp. 5793-5798 ◽  
Author(s):  
Zhaomin Yang ◽  
Xiaoyuan Ma ◽  
Leming Tong ◽  
Heidi B. Kaplan ◽  
Lawrence J. Shimkets ◽  
...  
Keyword(s):  
Cell Surface ◽  
Myxococcus Xanthus ◽  
Bacterial Chemotaxis ◽  
Type Iv Pili ◽  
Gliding Motility ◽  
Genetic Studies ◽  
Developmental Defects ◽  
Bacterial Surface ◽  
Type Iv ◽  
Cell Surface Structures

ABSTRACT Myxococcus xanthus social (S) gliding motility has been previously reported by us to require the chemotaxis homologues encoded by the dif genes. In addition, two cell surface structures, type IV pili and extracellular matrix fibrils, are also critical to M. xanthus S motility. We have demonstrated here that M. xanthus dif genes are required for the biogenesis of fibrils but not for that of type IV pili. Furthermore, the developmental defects of dif mutants can be partially rescued by the addition of isolated fibril materials. Along with the chemotaxis genes of various swarming bacteria and the pilGHIJ genes of the twitching bacteriumPseudomonas aeruginosa, the M. xanthus dif genes belong to a unique class of bacterial chemotaxis genes or homologues implicated in the biogenesis of structures required for bacterial surface locomotion. Genetic studies indicate that the dif genes are linked to theM. xanthus dsp region, a locus known to be crucial forM. xanthus fibril biogenesis and S gliding.

scholarly journals Role of Cell Surface Structures in Biofilm Formation by <i>Escherichia coli</i>

2015 ◽  
Vol 06 (12) ◽  
pp. 1160-1165 ◽  
Author(s):  
Hafida Zahir ◽  
Hamadi Fatima ◽  
Lekchiri Souad ◽  
Mliji El Mostafa ◽  
Ellouali Mostafa ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Cell Surface ◽  
Biofilm Formation ◽  
Surface Structures ◽  
Cell Surface Structures

scholarly journals The role ofCaulobactercell surface structures in colonization of the air-liquid interface

2019 ◽  
Author(s):  
Aretha Fiebig
Keyword(s):  
Cell Surface ◽  
Caulobacter Crescentus ◽  
Three Dimensional ◽  
Liquid Interface ◽  
Type Iv Pili ◽  
Surface Structures ◽  
Aquatic Environments ◽  
Type Iv ◽  
Biofilm Development ◽  
Air Liquid Interface

AbstractIn aquatic environments,Caulobacterspp. are often present at the boundary between liquid and air known as the neuston. I report an approach to study temporal features ofCaulobacter crescentuscolonization and pellicle biofilm development at the air-liquid interface, and have defined the role of cell surface structures in this process. At this interface,C. crescentusinitially forms a monolayer of cells bearing a surface adhesin known as the holdfast. When excised from the liquid surface, this monolayer strongly adheres to glass. The monolayer subsequently develops into a three-dimensional structure that is highly enriched in clusters of stalked cells known as rosettes. As this pellicle film matures, it becomes more cohesive and less adherent to a glass surface. A mutant strain lacking a flagellum does not efficiently reach the surface, and strains lacking type IV pili exhibit defects in organization of the three-dimensional pellicle. Strains unable to synthesize holdfast fail to accumulate at the boundary between air and liquid and do not form a pellicle. Phase contrast images support a model whereby the holdfast functions to trapC. crescentuscells at the air-liquid boundary. Unlike the holdfast, neither the flagellum nor type IV pili are required forC. crescentusto partition to the air-liquid interface. While it is well established that the holdfast enables adherence to solid surfaces, this study provides evidence that the holdfast has physicochemical properties required for partitioning of non-motile mother cells to the air-liquid interface, which facilitates colonization of this microenvironment.ImportanceIn aquatic environments the boundary at the air interface is often highly enriched with nutrients and oxygen. Colonization of this niche likely confers a significant fitness advantage in many cases. This study provides evidence that the cell surface adhesin known as a holdfast enablesCaulobacter crescentusto partition to and colonize the air-liquid interface. Additional surface structures including the flagellum and type IV pili are important determinants of colonization and biofilm formation at this boundary. Considering that holdfast-like adhesins are broadly conserved inCaulobacterspp. and other members of the diverse classAlphaproteobacteria, these surface structures may function broadly to facilitate colonization of air-liquid boundaries in a range of ecological contexts including freshwater, marine, and soil ecosystems.

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